In the hallway of Bidzina Ivanishvili's extraordinary glass home is a work by Gilbert & George. It is to Ivanishvili's credit that he agrees to be photographed next to it and a slogan that reads: "SAY FUCK OFF TO RICH BASTARDS." Ivanishvili is, after all, worth $6.4bn (£3.9bn), and one of the richest bastards, or successful businessmen, on the planet.

His possessions include a zoo with penguins, lemurs and a zebra, kept at his village in western Georgia, and a large collection of modern art. There are sculptures by Henry Moore (the art works dotted around his residence are all fake, the originals "kept safe" in a London vault). His home is a striking one-off – a James Bond-like space-age palace of steel and tubular columns, with panoramic views of Georgia's twinkling capital Tbilisi. Aides nickname it the 'glassle'. There is also fleet of black Land Cruisers.

The one thing that Ivanishvili doesn't have is power. Or at least not yet. In October 2011 the Georgian billionaire dramatically and unexpectedly entered politics, challenging the country's president Mikheil Saakashvili in a battle that has become increasingly nasty and personal. Ivanishvili charges that Saakashvili - who swept to power in 2003 during the rose revolution - has morphed into a dictator. On Monday, Georgians vote in a epochal parliamentary election. The choice is between Saakashvili's ruling party and Ivanishvili's anti-government Georgia Dream coalition.

As Ivanishvili tells it, it was Saakashvili's despotic behaviour that forced him into politics. "I'm 56 years old. I decided to go into politics because of our Soviet-style government," he says. The tycoon says that in 2008 Saakashvili "bought" off Georgia's old parliamentary opposition, forcing him to forge a new alliance last year with the country's surviving independent political forces.

In an interview on Sunday evening with several international newspapers including the Guardian, Ivanishvili complains bitterly of the persecution he has endured ever since. The state has stripped him of his Georgian citizenship. Several of his activists have been arrested. He even hints that Saakashvili is personally capable of dark deeds. "I'm very happy that I'm physically alive. We could have experienced pretty much everything from this government," he says, flanked by members of his opposition team.

Despite his loathing for Georgia's president, however, Ivanishvili's policies seem rather similar. On foreign policy, he says this: "Our policy is European and Euro-atlantic integration. There is no substitute for Nato." The pro-western Saakshvili's believes the same: it was his desire to join Nato that contributed to the Kremlin's crushing invasion of Georgia in 2008, following the president's doomed attempt to wrest back breakaway South Ossetia.

Ivanishvili has previously stated that Vladimir Putin's Russia is now freer than Saakashvili's Georgia. Asked about this, Ivanishvili gets irritated; his response surprisingly thin-skinned. The government has painted Ivanishvili as a Russian agent and the accusation clearly grates. He made his fortune in Russia in the 1990s (banking, pharmacy, real estate) but says he has now sold off two-thirds of his Russian assets; he still has a significant chunk of Gazprom. "You journalists are always asking about Russia," he says.

But how might he improve relations with the prickly Putin, the man who promised to hang Georgia's current president "by the balls"? "I think it's important to reinstate cultural and commercial relations," he says. And what about Abkhazia and South Ossetia, the two rebel regions occupied by Russian tanks, and recognised by Moscow as "independent" following the 2008 war? "When it comes to reinstating territorial integrity this will be a very hard and long task. I don't have illusions it will happen easily," he admits.

In the run-up to the election, Transparency International has accused both sides of presenting "simplistic programmes", promising large investments in agriculture, education, healthcare and social benefits. Critics say Ivanishvili's plan is vague, incoherent even. The billionaire says he main priority is jobs; certainly ordinary Georgian voters complain of high unemployment, low pensions and a lack of opportunities. He points out that unlike Saakashvili he understands business.

Western diplomats in Tbilisi fear that if Ivanishvili's coalition loses his supporters will take to the streets, with weeks of turmoil to follow. Ivanishvili, however, says his movement is peaceful. If international observers - currently packing out Tbilisi's al fresco restaurants - certify the election as free and fair he will accept the result; his coalition will form the parliamentary opposition. "Without doubt," he emphasises in English. He's more comfortable, though speaking in Georgian or Russian.

Interview over, we troop out past the Gilbert & George fake, and admire the stunning view from his terrace as the sun sets over a picture postcard Tbilisi. Ivanishvili points to the giant sphere hovering as if in mid-air inside his palace. "It's actually a cafe. You can fit 150 people inside," he says. Behind his residence is Tbilisi's wild botanical garden; Ivanishvili's private quarters resemble an inverted flying saucer about to take off. The billionaire says he's been to London twice but hasn't met Tony Blair or David Cameron.

And what about his zoo? Saakashvili's aides say the penguins are evidence of his eccentricity. Actually, it appears he is genuinely fond of his animals. "I bought my penguins from a zoo in France. I've got four of them," he says. He admits Georgia's warm climate is not really "sustainable" for his pet zebra and says he likes his lemurs. "They're like cats really. But I haven't got a big zoo." As well as his bid to defeat Georgia's president, Ivanishvili has another problem: too many deer. His small herd keeps on breeding, he says. "Would you like to take a deer home?" he asks with a smile.